Social stress contributes to the expression and potentiation of symptoms underlying severe psychiatric disorders. Previous research suggests that social stress evokes significant alterations in the activity of monoamine neurotransmitters such as serotonin (5HT) and dopamine (DA) within the limbic system of the brain. Changes monoamine activity also appear to be a major component of psychiatric disorder pathology. However, it is unclear whether the perception of social stress or the production of the behavioral response to these stressors, or both, are being mediated by limbic monoamine activity. Also, within the limbic system itself, amygdalar activity is known to alter DA release in the nucleus accumbens (NAc). This interaction appears to have relevance for limbic monoamine mediation of social stress, but the mechanisms are not well understood. This project will employ a reptile model of social stress to explore monoamine interactions between these two limbic areas, in addition to investigating the monoaminergic correlates of both perception of social stress and the production of behaviors during stressful social interactions. The proposed studies will first measure changes in NAc DA in response to increased 5HT within the amygdala (designed to mimic 5HT increases seen during social stress), using in vivo chronoamperometry in anesthetized lizards. Subsequent experiments utilizing similar methodology will then determine whether the inhibitory neurotransmitter GABA mediates 5HT-induced alteration of NAc DA activity. The temporal nature of changes in amygdala 5HT and NAc DA activity occurring during a stressful social interaction will also be investigated. To achieve this, male lizards will be presented with video stimuli of aggressively behaving opponents, manipulated to represent varying levels of social threat. Brains will be collected from animals upon perception of the social threat before production of any behavioral response, and from a separate group of animals allowed to produce social responses. The amygdala and NAc will be subsequently microdissected, with HPLC used to determine whether monoamine activity in each region changes as a function of perception versus response production during social stress. Findings from these studies are anticipated to have implications for further understanding the neural bases of maladaptive behaviors arising from either the perception of social stress or inappropriate responding in social situations.